Disgraced MP David Garrett will reveal the inside story of the strife within the Act Party in an interview to be published tomorrow, it was reported tonight.

Mr Garrett, who is expected to resign from Parliament tomorrow after quitting ACT over the passport fraud scandal, has given an exclusive interview to the Truth Weekender newspaper, TV3 News reported.

"In the interview Garrett talks about the dark forces within ACT and the `thrill' of securing the birth certificate of the dead infant 26 years ago," the report said.

"He takes a shot at ACT's former deputy Heather Roy and her adviser Simon Ewing-Jarvie."

Mrs Roy lost the deputy leadership last month and Mr Ewing-Jarvie leaked damaging notes she had prepared for her defence, in which she accused party leader Rodney Hide of bullying her.

In the newspaper interview Mr Garrett describes his ordeal over the passport as "bloody awful" and says he "went down in flames" because he was a supporter of Mr Hide, the TV3 report said.

Mr Garrett resigned from ACT last week over the revelations that he used the identity of a dead infant to get a false passport in 1984.

He was prosecuted for the offence in 2005, and was discharged without conviction.

Mr Garrett made his admission in a statement to Parliament and since then has been under attack from opposition parties.

Prime Minister John Key and Labour leader Phil Goff have both said he should quit Parliament, and he is expected to do that tomorrow by sending a letter to Speaker Lockwood Smith.

Mr Hide knew about the passport offence before Mr Garrett became an ACT candidate in 2008, and questions have been raised in Parliament about the party leader's judgment and behaviour.

Labour has severely criticised Mr Hide, accusing him of covering up the offence and calling on Mr Key to remove his local government ministerial portfolio.

Mr Key is not going to do that, and told Parliament today "in all my dealings with him as a minister he has been honest and trustworthy with me".